NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

System Advisor Model, SAM 

2014.1.14: General Description

Nate Blair, Aron P. Dobos, Janine Freeman, 

Ty Neises, and Michael Wagner

National Renewable Energy Laboratory

Tom Ferguson, Paul Gilman, and Steven 

Janzou

Independent Consultants

Technical Report

NREL/TP-6A20-61019

February 2014
NREL is a national laboratory of the U.S. Department of Energy

Office of Energy Efficiency & Renewable Energy

Operated by the Alliance for Sustainable Energy, LLC

This report is available at no cost from the National Renewable Energy

Laboratory (NREL) at www.nrel.gov/publications.

Contract No. DE-AC36-08GO28308

National Renewable Energy Laboratory

15013 Denver West Parkway

Golden, CO 80401

303-275-3000 • www.nrel.gov

System Advisor Model, SAM 

2014.1.14: General Description

Nate Blair, Aron P. Dobos, Janine Freeman, 

Ty Neises, and Michael Wagner

National Renewable Energy Laboratory

Tom Ferguson, Paul Gilman, and Steven 

Janzou

Independent Consultants

Prepared under Task No. SS13.5020

Technical Report

NREL/TP-6A20-61019

February 2014
NOTICE

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Cover Photos: (left to right) photo by Pat Corkery, NREL 16416, photo from SunEdison, NREL 17423, photo by Pat Corkery, NREL 

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Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.
iii

Executive Summary

This document describes the capabilities of the U.S. Department of Energy and National 

Renewable Energy Laboratory's System Advisor Model (SAM), Version 2014.1.14, released on 

January 14, 2014, for potential users or readers wanting to learn about the model's capabilities. 

SAM is a computer model that calculates performance and financial metrics of renewable energy 

systems. Project developers, policymakers, equipment manufacturers, and researchers use SAM 

results to evaluate financial, technology, and incentive options for renewable energy projects. 

SAM simulates the performance of photovoltaic, concentrating solar power, solar water heating, 

wind, geothermal, biomass, and conventional power systems. The financial model can represent 

financial structures for projects that either buy and sell electricity at retail rates (residential and 

commercial) or sell electricity at a price determined in a power purchase agreement (utility). 

SAM's advanced simulation options facilitate parametric and sensitivity analyses, and statistical 

analysis capabilities are available for Monte Carlo simulation and weather variability (P50/P90) 

studies. SAM can also read input variables from Microsoft Excel worksheets. For software 

developers, the SAM software development kit (SDK) makes it possible to use SAM simulation 

modules in their applications written in C/C++, C#, Java, Python, and MATLAB. NREL 

provides both SAM and the SDK as free downloads at http://sam.nrel.gov. Technical support and 

more information about the software are available on the website.

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
iv

Table of Contents

SAM Overview ............................................................................................................................................. 1

Model Structure........................................................................................................................................... 3

SAM Software Development Kit ........................................................................................................... 3

SAM Models and Databases .................................................................................................................. 3

Results: Tables, Graphs, and Reports...................................................................................................... 5

Performance Models................................................................................................................................... 6

Financial Models ......................................................................................................................................... 8

Residential and Commercial Projects..................................................................................................... 8

Power Purchase Agreement (PPA) Projects........................................................................................... 8

Levelized Cost of Energy and Cash Flow .............................................................................................. 9

Incentives.............................................................................................................................................. 10

Analysis Options....................................................................................................................................... 11

Software Development History and Users ............................................................................................. 12

Downloading SAM and User Support ..................................................................................................... 13

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
v 

List of Figures

Figure 1. The SAM main window showing monthly electricity generation and the annual cash 

flow for a photovoltaic system ...................................................................................................2

Figure 2. The Results page showing the energy loss diagram for a photovoltaic system ...............5

Figure 3. The Time Series graph on the Results page showing hourly electricity generation for 

a 100 MW parabolic trough system with 6 hours of storage .....................................................6

Figure 4. The first several rows of the cash flow table for a utility-scale project ...........................9

Figure 5. The report generator exports a PDF showing key assumptions and results from a 

SAM analysis case ...................................................................................................................12

Figure 6. SAM's help system includes detailed descriptions of the user interface, modeling 

options, and results...................................................................................................................13

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
1 

SAM Overview

This document describes the U.S. Department of Energy and National Renewable Energy 

Laboratory's System Advisor Model (SAM), Version 2014.1.14, released on January 14, 2014. It 

is intended to both help potential users determine whether the model meets their modeling needs, 

and provide information for readers who do not plan to use the model but want to learn about 

its capabilities. 

SAM is a performance and financial model designed to facilitate decision making for people 

involved in the renewable energy industry: 

• Project managers and engineers

• Financial and policy analysts

• Technology developers

• Researchers. 

SAM makes performance predictions and cost of energy estimates for grid-connected power 

projects based on installation and operating costs and system design parameters that you specify 

as inputs to the model. Projects can be either on the customer side of the utility meter, where they 

buy and sell electricity at retail rates, or on the utility side of the meter, where they sell electricity 

at a price negotiated through a power purchase agreement (PPA). 

SAM is an electric power generation model and assumes that the renewable energy system 

delivers power either to an electric grid, or to a grid-connected building or facility to meet 

electric load. It does not model thermal energy systems that meet a thermal process load. SAM 

also does not model isolated or off-grid power systems, and does not model systems with 

electricity storage batteries.

Creating a SAM file involves choosing both a performance model and a financial model to 

represent your project. SAM automatically populates input variables with a set of default values 

based on your choices. After you create the file, you modify the inputs to provide information 

about the project's location, the type of equipment in the system, the cost of installing and 

operating the system, and financial and incentives assumptions. It is your responsibility as an 

analyst to review and modify all of the input data as appropriate for each analysis. Once you are 

satisfied with the input variable values, you run simulations, and then examine results. A typical 

analysis involves running simulations, examining results, revising inputs, and repeating that 

process until you understand and have confidence in the results.

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
2 

Figure 1. The SAM main window showing monthly electricity generation and the annual cash flow 

for a photovoltaic system

SAM is available as a desktop application for Windows and OS X. The National Renewable 

Energy Laboratory (NREL) distributes SAM for free at https://sam.nrel.gov. You may use SAM 

for any purpose, but you must acknowledge your use of SAM in any documentation of analysis 

involving the software, and credit NREL for developing the software, and the U.S. Department 

of Energy for supporting its development. Guidelines for citing SAM in publications are 

available at https://sam.nrel.gov/content/sam-publications. 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
3 

Model Structure

SAM consists of a user interface, calculation engine, and programming interface. The user 

interface is the part of SAM that you see. It provides access to input variables and simulation 

controls and displays tables and graphs of results. 

The user interface performs three basic functions:

• Provide access to input variables, which are organized into input pages. The input 

variables describe the physical characteristics of a system, and the cost and financial 

assumptions for a project. SAM's input variables are populated with default values to 

help you get started with your analysis. 

• Allow you to control how SAM runs simulations. You can run a basic simulation, or 

more advanced simulations for optimization and sensitivity studies. 

• Provide access to output variables in tables and graphs on the Results page, and in files 

that you can open in a spreadsheet application or other software. 

SAM's calculation engine, called the SAM Simulation Core (SSC), performs a time-step-bytime-step simulation of a power system's performance, and calculates project cash flow and 

financial metrics annually. The programming interface allows external programs to interact with 

SAM, and a public version is available in the SAM software development kit. 

SAM Software Development Kit

The SAM Simulation Core (SSC) software development kit (SDK) is a package of tools for 

software developers for creating renewable energy system and project models using the SSC 

library. The SSC library is the collection of simulation and computation modules that SAM uses 

to simulate renewable energy projects: SAM is a desktop application that provides a userfriendly front end for the SSC library. The SDK allows you to use modules from the SSC library 

in Windows, OS X, or Linux applications that you write in C++, C#, Java, MATLAB, or Python. 

NREL distributes the SAM Simulation Core SDK for free at https://sam.nrel.gov. 

SAM Models and Databases

SAM represents the cost and performance of renewable energy projects using computer models 

developed at NREL, Sandia National Laboratories, the University of Wisconsin, and other 

organizations. Each performance model represents a part of the system, and each financial model 

represents a project's financial structure. 

Source code for the SAM simulation and calculation modules is not available to the public. 

However, reference manuals describing the algorithms in each of the performance model 

modules are available for download from the SAM website. 

The models require input data to describe the performance characteristics of physical equipment 

in the system, and project costs and financial assumptions. SAM's user interface makes it 

possible for people with no experience developing computer models to build a model of a 

renewable energy project, and to make cost and performance projections based on model results. 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
4 

To describe the renewable energy resource and weather conditions at a project location, SAM 

requires a weather data file. Depending on the kind of system you are modeling, you either 

choose a weather data file from a list, download one from the Internet, or create the file using 

your own data. 

SAM includes several libraries of performance data and coefficients that describe the 

characteristics of system components such as photovoltaic modules and inverters, parabolic 

trough receivers and collectors, wind turbines, and biopower combustion systems. For those 

components, you simply choose an option from a list, and SAM applies values from the library 

to the input variables.

SAM can automatically download data and populate input variable values from the following 

online databases:

• DSIRE for U.S. incentives. 

• OpenEI Utility Rate Database for retail electricity rate structures for U.S. utilities. 

• NREL Solar Prospector for solar resource data and ambient weather conditions. 

• NREL Wind Integration Datasets for wind resource data. 

• NREL Biofuels Atlas and DOE Billion Ton Update for biomass resource data.

• NREL Geothermal Resource database for temperature and depth data. 

For the remaining input variables, you either use the default value or change its value. Some 

examples of input variables are:

• Installation costs including equipment purchases, labor, engineering and other project 

costs, land costs, and operation and maintenance costs.

• Numbers of modules and inverters, tracking type, and derating factors for photovoltaic 

systems.

• Collector and receiver type, solar multiple, storage capacity, and power block capacity 

for parabolic trough systems. 

• Analysis period, real discount rate, inflation rate, tax rates, internal rate of return target or 

power purchase price for utility financing models. 

• Building load and time-of-use retail rates for commercial and residential financing 

models. 

• Tax and cash incentive amounts and rates. 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
5 

Results: Tables, Graphs, and Reports

SAM displays modeling results in tables and graphs, ranging from the metrics table that displays 

levelized cost of energy, first year annual production, and other single-value metrics, to tables 

and graphs that show detailed annual cash flows and hourly performance data. 

Figure 2. The Results page showing the energy loss diagram for a photovoltaic system

After you run simulations, SAM displays a set of default graphs. You can customize the graphs 

by changing titles, colors, and font sizes, or create new graphs that show different data. You can 

also export images of all graphs and the data they display to include in reports and presentations, 

or to analyze further with other software. 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
6 

Performance Models

SAM's performance models make hour-by-hour calculations of a power system's electric output, 

generating a set of 8,760 hourly values that represent the system's electricity production over a 

single year. You can explore the system's performance characteristics in detail by viewing tables 

and graphs of the hourly and monthly performance data, or use performance metrics such as the 

system's total annual output and capacity factor for more general performance evaluations. 

Figure 3. The Time Series graph on the Results page showing hourly electricity generation for a 

100 MW parabolic trough system with 6 hours of storage 

The current version of SAM includes performance models for the following technologies: 

• Photovoltaic (PV) systems (flat-plate and concentrating photovoltaic) 

• CSP parabolic trough 

• CSP power tower (molten salt and direct steam)

• CSP linear Fresnel

• CSP dish-Stirling

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
7 

• Conventional thermal (a simple heat rate model)

• Solar water heating for residential or commercial buildings

• Large and small wind power 

• Geothermal power and geothermal co-production 

• Biomass power. 

You can compare different kinds of projects by creating more than one case in a file. For 

example, you could compare the savings of a residential rooftop solar water heater to those of a 

photovoltaic system. Or, for a large utility-scale project, you could compare the power purchase 

price that would be required to make a wind, a photovoltaic, or a concentrating solar power 

project profitable at a given location. SAM does not model hybrid power systems. For example, 

you cannot model a single project that combines wind turbines and photovoltaic modules. 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
8 

Financial Models

SAM's financial models calculate financial metrics for various kinds of power projects based on 

a project's cash flows over an analysis period that you specify. The financial model uses the 

system's electrical output calculated by the performance model to calculate the series of annual 

cash flows.

SAM includes financial models for the following kinds of projects: 

• Residential (retail electricity rates)

• Commercial (retail rates or power purchase agreement)

• Utility-scale (power purchase agreement):

o Single owner 

o Leveraged partnership flip 

o All equity partnership flip

o Sale leaseback. 

Residential and Commercial Projects

Residential and commercial projects are financed through either a loan or cash payment, and 

recover investment costs through savings from reduced electricity purchases from the electricity 

service provider. For electricity pricing, SAM can model simple flat buy and sell rates, monthly 

net metering, or complex rate structures with tiered time-of-use pricing. For these projects, SAM 

reports the following metrics:

• Levelized cost of energy

• Electricity cost with and without renewable energy system

• Electricity savings

• After-tax net present value 

• Payback period. 

Power Purchase Agreement (PPA) Projects

Utility and commercial PPA projects are assumed to sell electricity through a power purchase 

agreement at a fixed price with optional annual escalation and time-of-delivery (TOD) factors. 

For these projects, SAM calculates:

• Levelized cost of energy

• PPA price (electricity sales price)

• Internal rate of return

• Net present value

• Debt fraction or debt service coverage ratio. 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
9 

SAM can either calculate the internal rate of return based on a power price you specify, or 

calculate the power price based on the rate of return you specify. 

Levelized Cost of Energy and Cash Flow

For projects using retail electricity rates (residential and commercial), SAM calculates the 

levelized cost of energy (LCOE) from after-tax cash flows, so that the LCOE represents the cost 

of generating electricity over the project life, accounting for taxes and incentives. For projects 

selling electricity under a power purchase agreement (utility), SAM calculates the LCOE from 

the revenue cash flow, so that the LCOE also includes the developer's margin defined by the 

project's internal rate of return. 

Figure 4. The first several rows of the cash flow table for a utility-scale project

The project annual cash flows include: 

• Revenues from electricity sales and incentive payments

• Installation costs

• Operating, maintenance, and replacement costs

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
10 

• Loan principal and interest payments 

• Tax benefits and liabilities (accounting for any tax credits for which the project 

is eligible)

• Incentive payments 

• Project and partner's internal rate of return requirements (for PPA projects). 

Incentives

The financial model can account for a wide range of incentive payments and tax credits: 

• Investment based incentives 

• Capacity-based incentives

• Production-based incentives 

• Investment tax credits

• Production tax credits

• Depreciation (MACRS, Straight-line, custom, bonus, etc.). 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
11 

Analysis Options

In addition to simulating a system's performance over a single year and calculating a project cash 

flow over a multi-year period, SAM's analysis options make it possible to conduct studies 

involving multiple simulations, linking SAM inputs to a Microsoft Excel workbook, and working 

with custom simulation modules. The following options are for analyses that investigate the 

impacts on model results of variations and uncertainty in assumptions about weather, 

performance, cost, and financial parameters:

• Parametric Analysis: Assign multiple values to input variables to create graphs and tables 

showing the value of output metrics for each value of the input variable. Useful for 

optimization and exploring relationships between input variables and results. 

• Sensitivity Analysis: Create tornado graphs by specifying a range of values for input 

variables as a percentage of a base value. 

• Statistical Analysis: Create histograms showing the sensitivity of output metrics to 

variations in input values. 

• Probability of Exceedance Analysis (P50/P90): For locations with weather data available 

for many years, calculate the probability that the system's total annual output will exceed 

a certain value.

SAM also makes it possible to work with external models developed in Excel or the TRNSYS 

simulation platform:

• Excel Exchange: Use Excel to calculate the value of input variables, and automatically 

pass values of input variables between SAM and Excel. 

• Exchange Variables: Create your own input variables for use with Excel Exchange or a 

custom TRNSYS deck.

• Simulator Options: Change the simulation time step, or run SAM with your own 

simulation modules developed in the TRNSYS modeling platform. 

Finally, SAM's scripting language SamUL allows you to write your own programs within the 

SAM user interface to control simulations, change values of input variables, and write data to 

text files.

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
12 

Software Development History and Users

SAM, originally called the "Solar Advisor Model," was first developed by the National 

Renewable Energy Laboratory in collaboration with Sandia National Laboratories in 2005 for 

internal use by the U.S. Department of Energy's Solar Energy Technologies Program in its 

systems-based analysis of solar technology improvement opportunities within the program. 

NREL released the first public version in August 2007 as Version 1, making it possible for solar 

energy professionals to analyze photovoltaic systems and concentrating solar power parabolic 

trough systems in the same modeling platform using consistent financial assumptions. Between 

2007 and 2013, two new versions were released each year, adding new technologies and 

financing options. In 2010, the name changed to "System Advisor Model" to reflect the addition 

of non-solar technologies. Beginning in 2014, NREL will release one new version of the 

software each year, with periodic maintenance updates as needed.

Figure 5. The report generator exports a PDF showing key assumptions and results from a SAM 

analysis case

The DOE and DOE laboratories continue to use the model for program planning and grant 

programs. Since the first public release, over 35,000 people have downloaded the software, 

representing manufacturers, project developers, academic researchers, and policymakers. 

Academic professionals use SAM for graduate-level classroom instruction and for research. 

Project developers use SAM to evaluate different system configurations to maximize earnings

from electricity sales. Policymakers and designers use the model to experiment with different 

incentive structures.

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
13 

Downloading SAM and User Support

SAM runs on both Windows and OS X. It requires about 500 MB of storage space on your 

computer. SAM is available for free download. To download the software, you must register for 

an account on the website. After registering, you will receive an email with your account 

information. SAM's website includes software descriptions, links to publications about SAM and 

other resources. 

Figure 6. SAM's help system includes detailed descriptions of the user interface, modeling 

options, and results

The following resources are available for learning to use SAM and for getting help with 

your analyses:

• Help system: Press the F1 key in Windows or Command-? in Mac OS from any input or 

results page in SAM to view the Help topic for that page.

• User support forum. 

• Documentation, videos, and training schedule on the SAM website Learning page. 

You can contact the SAM support team by submitting a message on the Contact Us page. 

This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.